Mikolaj Pietrzak is a Warsaw-based advocate specialising in criminal law and human rights. A partner in the Pietrzak Sidor & Partners Law Office in Warsaw, Mikolaj is a council member of the Warsaw Bar Association and the Chairman of the Human Rights Committee of the National Bar Council of Poland. He is a member of the European Criminal Bar Association and an international member of the Perren Buildings Chambers in London.

Mikolaj specialises in criminal law and the protection of human rights, and has experience in a wide range of legal work including defending European Arrest Warrant cases. He has appeared before the Supreme Court of Poland, the Constitutional Tribunal of Poland and represented applicants before the European Court of Human Rights. He is currently the representative of Guantanamo detainee Abd al-Rahim Al-Nashiri in the criminal investigation conducted by the Appellate Prosecutor in Warsaw concerning the operation of the CIA secret prison in Poland, the detainment and torture therein of Al-Nashiri and other CIA prisoners, and the related abuse of power by public officials in Poland. In 2013, Mikolaj received the Edward J. Wende Award, which recognises lawyers who dedicate themselves to the fight for justice and defence of the public good.